1. Field of the Invention
The present invention relates to rotor shafts and, more particularly, to support and drive arrangements suited for helicopter rotors.
2. Description of the Prior Art
Over the years various arrangements have been proposed to support and transmit torque to a rotary shaft.
For instance, a helicopter mast is typically driven by an engine via a separate rotor transmission attached to the helicopter airframe by a relatively complex articulated, flexible mounting structure. The mounting structure must be designed to control the transmission of rotor flight and dynamic loads to the airframe. It would be beneficial to have a new arrangement in which the transmission would be integrated to the engine and mounted to the airframe via a simple mounting structure adapted to reduce airframe vibrations.
In certain applications where a rotor is subject to radial excursion such as by vibration, it has been proposed to use squeeze-film bearing dampers to accommodate certain radial motion caused by high-speed rotor dynamics. Typically, a damping fluid, such as oil, is introduced into an annular chamber surrounding the bearing supporting the rotor. Radial motion of the bearing together with the rotor relative to the annular chamber creates hydrodynamic forces opposing the radial motion of the bearing. The shearing action occurring upon the oil effectively dampens the radial motion.
Although such squeeze-film bearings are efficient to dampen high frequency, low energy vibrations, it has been found that there is a need for a new fluid damper which is adapted to accommodate rotor vibrations of lower frequency and higher energy.
It has also been found that there is a need for a new transmission arrangement which is adapted to accommodate radial motion of a rotary shaft while ensuring torque transmission thereto.
It is therefore an aim of the present invention to provide a new fluid damping bearing apparatus which provides improved damping capacity.
It is also an aim of the present invention to provide a new transmission arrangement which is adapted to compensate for rotor misalignment.
It is a further aim of the present invention to provide a new helicopter rotor support and drive arrangement.
Therefore, in accordance with the present invention, there is provided a fluid damper for absorbing radial motion of a bearing supporting a rotary shaft, comprising a number of circumferentially distributed fluid containing cylinders adapted to be concentrically placed about a bearing, each said fluid cylinder being radially oriented relative to the bearing and defining a chamber in which a piston is slidably displaceable against a damping fluid to oppose a radial movement of the bearing.
In accordance with a further general aspect of the present invention, there is provided a drive connection for a rotor shaft, comprising a driving member having a first meshing structure, a driven member adapted to rotate with a rotor shaft and having a second meshing structure, and an intermediate diaphragm coupling adapted to be mounted about the rotor shaft and having third and fourth meshing structures flexibly connected to each other for meshing engagement, respectively, with said first and second meshing structures for enabling said driven member to rotate with said driving member.
According to a further general aspect of the present invention, there is provided a helicopter rotor support and drive arrangement, comprising a stationary housing adapted to be rigidly mounted to an airframe of a helicopter, a helicopter rotor extending through said stationary housing, bearings for rotatably supporting said helicopter rotor in said stationary housing, a fluid damping structure for accommodating radial motion of said helicopter rotor relative to said stationary housing, a driving member mounted in said stationary housing and having a first meshing structure, a driven member for rotation with said helicopter rotor and having a second meshing structure, and an intermediate diaphragm coupling mounted about said helicopter rotor and having third and fourth axially spaced-apart meshing structures flexibly connected to each other for meshing engagement, respectively, with said first and second meshing structures to transmit a torque from said driving member to said driven member and said helicopter rotor.